Performance testing of clonal Oreochromis niloticus lines

Six different homozygous clonal lines (343 adult fish) were established by gynogenetic reproduction of mitotic gynogenetic Oreochromis niloticus femal es. Second generation clones (494 adult fish) were obtained by gynogenetic reproduction of clonal females. The clonal status of the fish was proven by the alloenzyme adenosine deaminase and DNA fingerprints. Performance testi ng of the all-female clonal groups was carried out in comparison with adequ ate heterozygous control,groups. Up to first feeding, clones showed a signi ficantly reduced mean survival rate (4.0%) if compared with offspring of no rmal heterozygous fish (43.9%). Reproductive traits of the second generatio n clones varied between and within clonal lines, Mean body weight differenc es at 136th day of life between all-female clonal groups (45.5 g), kept und er three different density classes, and corresponding all-female heterozygo us control groups (50.2 g) were not significant. Variation of body weight w as significantly lower in all-female homozygous clones (coefficient of vari ation: 23.1%) than in all-female heterozygous controls (coefficient of vari ation: 34.1%). Possible reasons for phenotypic variation between isogenic O . niloticus individuals are discussed. (C) 2000 Elsevier Science B.V. All r ights reserved.